Patent GB-771680-A (GB)
Title: Improvements in and connected with electric tracer control systems for manufacturingmachines
IPC: B23Q35/122
Filed: 1954-02-12
Abstract: 771,680. Electric control systems. SCHMID, W. K. Feb. 12, 1954 [Feb. 13, 1953], No. 4173/54. Class 40 (1). In a tracer controlled copying machine, the tracer shaft carries a tracer roller positively driven to roll along a template contour substantially without slip, the tracer shaft being capable of limited universal movement and being deflected by the roller movements to control two co-ordinate drive motors which move the cross-slide carrying the feeler head to follow the tracer roller movements. The template and roller are preferably magnetic. As shown, the tracer head 15, Fig. 1, is carried by a support 14 movable along a guide rail 11 in the direction C-D through a rack 12 and pinion drive by a motor 13. The guide rail 11 is carried by a cross-slide 8 movable along guide rails 6, 7 in the direction A-B by a motor 10 driving a pinion meshing with a rack 9 on the guide 6. The magnetic tracer roller is rotated by a separate motor 17 to roll around the contour of a magnetic template 19 and controls the co-ordinate motors 13, 10 so that the tracer head follows the movements of the tracer roller and causes a welding torch 22 carried by a bar 23 secured to the support 14 to cut the shape of the template from a workpiece 21. Tracer head, construction, Fig. 2. The constant speed motor 17 drives the tracer roller 16 through a Cardan or flexible shaft 24, the tracer shaft 25 and with it the tracer casing 26 being capable of limited linear movement relative to the frame 15 in the co-ordinate directions A-B, C-D against the action of biasing springs 39-40-43-44, 41-42-45- 46 which are adjustable to define the neutral or 0-0 position of the tracer shaft 25. Deflections of the tracer shaft in the directions A-B, C-D are sensed by contact arms 48, 51 secured to the tracer casing 26, disposed at right angles to each other, and wiping over respective quadrature contact banks 49, 52 secured to the frame 15. The tracer roller is preferably magnetic, the energizing coil therefor being housed in the easing 26. Control circuitry, Fig. 2. The contact banks 49, 52 each consist of a zero position and four contacts I-IV, I<SP>1</SP>-IV<SP>1</SP>, on opposite sides thereof. As the contact arm 48, for example, wipes over contacts I-IV relays R1-R4 respectively are energized and effect a stepped increase in speed of the co-ordinate motor 13 in the follow-up direction. The motor has a three-phase stator and a wound rotor adapted to be short circuited periodically through conically-shaped conducting portions 62, 63 . . . &c. on a constant speed drum 61, over brushes 69, 70, 71 respectively when relays R1, R2, R3 are energized. The time during each rotation of the drum for which the rotor is short circuited is thus increased as the relays R1, R2, R3 are sequentially operated and so increases the motor speed. Full speed is effected by relay R4 which directly short circuits the rotor. If the contact arm 48 is deflected in the opposite sense-over contacts I<SP>1</SP>-IV<SP>1</SP>-a reversing relay R5 is energized in position I<SP>1</SP> to reverse the stator connections through a relay 58 so that the motor 13 is driven in the reverse direction. Speed control is effected as before by relays R1 . . . R4. The reversing relay R5 locks until the contact arm 48 returns to normal when it is released by a relay R6. The co-ordinate motor 10 is similarly controlled over the contact bank 52 by relays R7 . . . R12. In a modification, Fig. 4 (not shown), the co-ordinate motors are speed controlled as above described but run in one direction only. They drive the associated pinions through reverse drive clutches.